Finished frontThis is the front of the house after the roof on this side had been finished.  It doesn't yet have the ridge tiles fitted, as they go on after the other side has been done.

As this took up so much of our time last year, I thought I might just run through some of the why's and wherefore's.  The trouble with doing these one off jobs (and no - I do not intend to repeat the project), is that you amass a great deal of knowledge and experience - and never use it again!  So maybe this might help somebody, somewhere, somewhen (as they used to say in Ringwood).

There many different types of roof structure but I thought I might run through a few as the differences are considerable.  It will also help understanding the photos that we took, which follow.  Our house was built sometime in the 17th century and in those days they used what was to hand - granite for the walls and oak for the timbers as they grow everywhere here.

roof trusses

Modern french roof construction - for all those lovely magnolia 'pavillons' that you see everywhere - is just like that used in the UK - pre-stressed trusses, assembled off-site and erected very quickly.

 

They have some disadvantages - loft access can be tricky for storage etc - and loft conversion even more so, as all the timbers play a significant, structural part to the whole and altering them is a job for the experts.

 

rafters

 

Historically simple UK roofs were constructed as shown here, so that the common rafters carried a substantial load and were therefore quite substantial timbers.  They took the weight of the slates or tiles, supported by purlins, if necessary.

Some houses are still built this way today but the contruction method is considerably more expensive - both in terms of material and the skilled trades needed to build them.

One big advantage is the ease of conversion - there are no obstructions in the roof space and few structural timbers need cutting (apart from window installation for example).

 

 

 

truss

 

Our roof follows the style of most of the old houses round here - with massive oak king post trusses.

The roof and attic are a straightforward 'toblerone' shape - a gable at each end with 3 trusses at equidistant intervals between them.  No valleys, hips or dormer windows.

The trusses carry 2 purlins (les pannes) each side and the rafters (les chevrons) are fixed to the ridge, purlins and wall plate.  The chevrons are much lighter than UK rafters, as the trusses and purlins carry much more of the weight.

There is good standing headroom right through the attic.  On the outside the roof measures just over 5 metres from ridge to gutter and 16 metres in length.  Altogether there were 162 m² (81m² per side) of roof surface to renew.

 

 

 

Roof structure

 

 

 

This photo taken in the attic (with half the slates off) gives a clear picture.  Luckily the weather was kind to us - and we picked our days carefully.

If you look at the top part of the roof (where there are still battens and slates), you'll see they didn't use roofing felt when the roof was last reslated.